Engines may utilize electrically actuated valves to enable improved engine operation in a variety of situation. For example, engine cylinders having a plurality of intake valves may operate under some conditions with multiple intake valves active, and under other conditions with one intake valve active. One such system is described in U.S. Pat. No. 7,213,548.
The inventors herein have recognized that air-fuel ratio excursions may occur during valve mode transitions, such as from dual intake valve operation (2V) to single intake valve operation (1V), such as alternating intake valve operation, in Electronic Valve Actuation (EVA) engines. In particular, the inventors have recognized that when a dual port configuration having an injector per cylinder centered over two ports, such transient fueling errors may be particularly prevalent. Various interrelated issues may be involved in creating the air-fuel ratio error. For example, in alternating intake valve operation, large fuel puddles and fuel vapors may develop in the deactivated port. While this can be addressed with alternating valve operation, such operation generates still further air-fuel ratio errors. For example, when a valve is deactivated, only a fraction of fuel may enter the cylinders on the first cycle after deactivation and some may remain in the deactivated port. This can produce a lean excursion in A/F. Likewise, when the valve is reactivated, the additional fuel left over from a previous cycle when the valve was deactivated may enter the cylinder, and a rich A/F spike may be produced.
As such, in one approach a method of control fueling of a cylinder in an internal combustion engine, the cylinder having at least two intake valves, may be used. The method may comprise operating in a first mode with one active intake valve and one inactive intake valve during a cycle of the cylinder; operating in a second mode with two active intake valves during a cycle of the cylinder; and adjusting a fuel injection from an injector configured to deliver fuel through at least the two intake valves, where the fuel injection adjustment is responsive to a transition in modes and based on whether the transition is from the first mode to the second mode, or from the second mode to the first mode.
In this way, it is possible to rapidly transition a plurality of engine cylinders between valve modes, such as between dual intake and alternating single intake valve modes, while reducing air-fuel ratio excursions, and uneven valve wear and deposits.